I dont glitch key, gawd.
I swear, the guy I played with taught me this way.
When you knife away from a wall, and run into it, you can see through part of it.
So to to complete the glitch, do this in succession(sp?):

Knife->Sprint->Jump.

For some of them it doesn't look like I sprint or jump but thats because Im crouching. I swear to god all of these work.